Speedwell Site-Specific
Ensemble Forecasts Speedwell site-specific ensemble forecasts are available for
over 100 sites across the world covering
15-day, monthly and seasonal periods. The
ensemble forecast is a fully downscaled probabilistic forecast
which inherently captures information that is normally lost in a traditional deterministic forecast:
the uncertainty of the forecast at each time step.
The product is based on the forecast models run by two of the world's leading numerical
prediction centres: the European Centre for Medium Range Weather Forecasting (ECMWF)
and the UK Met Office. The ECMWF forecast is produced as a granular, grid-based
output which need to be "ownscaled" to produce the site-specific forecasts which
are critical for energy demand modelling and for weather derivative trading. This
downscaling process is a critical part of the processing and is run on our behalf
by the UK Met Office using proprietary
Speedwell climatologies. The downscaling
uses the Met Office's Single Site model which takes into account such small-scale
features as topography, land type and the impact of wind effects. In respecting
the particular local conditions by further modelling in this way, a more accurate
forecast can be produced than by methods relying on MOS ( "odel output statistics" ).
An ensemble forecast comprises
a number of "embers", each of which can be viewed as a separate forecast. Each
member is derived from multiple runs of the same forecast model by modifying the
starting conditions of the climate model within the likely error parameters of the
those starting conditions. Under certain situations, these changes of conditions
can produce a big change in forecast outcomes (high uncertainty). At other times,
these changes have little impact (low uncertainty). This allows the user to understand
how much the forecast can be
How is the forecast viewed?..Graphically and Underlying Data
Data Feed File via FTP
The forecast is available in graphical and tabular formats through the Speedwell
website and as a data feed. The data feed delivers the underlying data for each member of the
forecasts via FTP.
The Speedwell forecast
may be viewed interactively in graphical and tabular format through the Speedwell
website (SpeedwellWeather.com).
Uniquely, the website also offers the user access
to
historical archives of forecasts as well as the means to overlay forecasts for
different sites, for different forecast periods and for different weather elements
(eg Tmin/Tmax/rain) with complete flexibility. Graphical images can easily be exported
and used in external documents (subject to Licence). Forecasts can be overlaid with
10-year smoothed average, previous years?value, actual outturn and forecast change
from previous run. Forecast error can also be shown permitting on-line verification
of forecasts to be performed.
Some examples of website outputs are shown below:
"Box plots" with Climate Average.
The Box Plot shows the average of all ensembles,
a box covering the mid quartiles, outliers and the smoothed 10-year climate average.
The box plots give a clear sense of the confidence in the forecast with tighter
boxes indicating less forecast uncertainty. Also shown below are thumbnails which
lead the user to a clear representation of the distribution of possible outcomes.
For each day, or in the case of the seasonal forecast, for each month, the various
forecasts implied by each member of the ensemble are shown in
a probability distribution graph. This gives very important information about the forecast. While a tight spread
shows a high degree of confidence, there are occasions when there is no single dominant
outcome.
The probability distribution graph drops each forecast
member into buckets. In the example shown it can be seen taht the average of the
forecast ( green line ) doese not correspond to the most probable outcome.
In certain cases, a bi-modal distribution might be shown. This might indicate
for instance that the Tmax outcome for a given day is actually as likely to be 24C
as 28C. A deterministic forecast would not be able to show this and would probably
suggest a value of 26C.
"Spaghetti" Graph.
The "spaghetti" graph gives a full sense
of the separate paths of each ensemble. Member 1 can be easily highlighted.
"Combination"
Graph
The "Combination" graph combines the average forecast with recent actual data
and last year's data for context.
Graphical Forecast Overlay
The data graphing options
available to the user are shown below. The background image shows monthly forecasts
for Tmin and Tmax with respective observed data and climatologies.
15-day forecast example showing a plot of the 51member forecast average for Tmax
and Tmin forecasts issued on 23rd March and on 4th April. Each shown with
15-day forecast example showing the overlay of TMax ensemble
average with observed data, last year's data and forecast forecast error(green).
Monthly forecast example showing a plot of the 51 member forecast average for TMax
shown with smoothed climatology and outturns.
Tabular Presentation
Speedwell forecasts are also available in tabular form through the website. The
table shown below presents user-selectable forecast information for a number of
sites simultaneously. Forecast average, median, volatility, difference from 10-year
average as well as HDD and CDD values are available.
The Single Site Daily Forecast
Table presents a range of forecast data for the site
selected by the user. For weather derivative traders, the example is of particular
interest as it shows the difference between HDD or CDD derived from the average
of the 51 members and that derived from taking the average HDD/CDD value using each
of the 51 members.
Our clients
Speedwell Ensemble Forecasts are used by energy and commodity
companies, banks and weather derivative market traders in Europe and the USA.
Becoming
a client
It is possible to experience the full flexibility of the Speedwell forecast
product on our website immediately. Go to SpeedwellWeather.com
and register for
a free trial. This will give access to a limited range of forecast sites while demonstrating
the comprehensive graphical viewing, overlay and forecast archive features. The
website also offers other unique free content including a weather derivative indicative
pricer and weather data viewing tools.
Speedwell are also happy to offer a free
trial of ensemble forecast products for specific sites. Please contact us for this
to be arranged. Please see the website for a full list of available forecast sites.
Forecast Verification
In addition to the verification which can be performed by
the user on the Speedwell website, we are able to provide verification statistics
on 15-day and monthly products.
Forecasts and Weather Derivatives
Speedwell Ensemble
Forecasts integrate automatically with the Speedwell Weather System (SWS) for pricing
weather derivatives. The user can select the forecast type to use and price both using the average of the forecast and by using each ensemble member separately to
correctly capture the convexity implicit in a probabilistic forecast. Please contact
us for more information
Contact Us
Regarding world-wide weather data and forecast
matters please see
www.SpeedwellWeather.com or contact:
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Phil Hayes
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phil.hayes@SpeedwellWeather.com |
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David Whitehead (U.S) |
david.whitehead@SpeedwellWeather.com |
Telephone:
UK office:
+44 (0) 1582 465 551
US office: +1 (0) 843 737 4843
Regarding software and consultancy
services please see
www.SpeedwellWeather.com or contact:
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Stephen Doherty
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stephen.doherty@SpeedwellWeather.com
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Dr Michael Moreno |
michael.moreno@SpeedwellWeather.com |
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David Whitehead (U.S) |
david.whitehead@SpeedwellWeather.com |
Telephone:
UK office: +44 (0) 1582 465 569
US office: +1 (0) 843 737 4843
Address
UK: Mardall House, Vaughan Rd, Harpenden, Herts, AL5 4HU
Address USA: 418 King St, Floor 2, Charleston, SC 29403 USA
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Documents
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